Phone will no longer connect to extender

  I recently upgraded my home router through my ISP (Spectrum). After this upgrade my extender (EX7500) needed to be reconnected, after doing so I found my PC and TV will connect just fine to the extended network unlike any phone (iPhones) that has tried to connect. If the phone will connect (95% of the time it flat out wont connect) it will show full signal but will not actually allow internet access while the other trick it has enjoyed playing is to show it is indeed connected but show no signal at all. It supposedly has the newest Firmware available, I've tried forgetting the network on phone, factory reset of network settings on phone, factory reset of extender, praying, bribing, nothing will work. I ensured my phone would connect to the router by directly connecting to it rather than the extender and it does connect directly to the router. I'd rather not rough up my extender but it is putting me into a corner with one way out, any suggestions?